A new spectrometer is ideal for pharma and more, says Rob Morris
Today’s compact spectrometers deliver signal to noise ratio (SNR) performance, optical resolution and acquisition speed comparable to more expensive and less flexible benchtop spectrometers. Here, we explore the absorbance linearity of the new Ocean HR2 spectrometer.
Absorbance of Bovine Serum Albumin
To evaluate the Ocean HR2, we measured nearly 30 different concentrations of 503mg bovine serum albumin (BSA) protein samples in distilled water. BSA is often used as a protein concentration standard in biochemical applications.
The setup comprised an Ocean HR2 spectrometer (190-880 nm), a deuterium light source with attenuator, a pair of 400 µm optical fibres, and a quartz cuvette in a cuvette holder. Operating software and OceanDirect, a device driver platform, completed the system.
To ensure the best measurement results, we first warmed up the spectrometer and light source for 30 minutes. Light source output can change slightly until the source is in thermal equilibrium, affecting measurements.
Also, as part of the sampling process, we never removed the quartz cuvette from the cuvette holder, as doing so can introduce errors. Instead, we made our dilutions in the cuvette, using a disposable pipet to remove some of each sample, then mixing in the DI water, and repeating the process for each sample.
Our measurements focused on the BSA absorbance peak at 280 nm (Fig. 1), which mapped to absorbance linearity of 0.999, up to 2.5 AU (Fig. 2). This level of performance would be beneficial in quantifying other types of protein concentration, as well as for biotechnology applications including quality assurance of pharmaceutical formulations.
Improving SNR
High Speed Averaging Mode is a hardware-accelerated signal averaging function accessible via the OceanDirect device driver that improves SNR performance in Ocean Insight spectrometers. With better SNR comes higher quality spectra and more accurate results.
SNR is a function of several factors, some more easily managed than others. For example, signal averaging to improve SNR can be carried out in operating software on the host computer but can take longer to process than what may be acceptable for your application. HSAM overcomes that limitation by enabling many more spectral averages over a given time period, yielding a much higher SNR per unit time. This can be important for time-critical or real-time applications, where decisions must be made very quickly and with high accuracy.
The advantage of HSAM can be quantified easily. For example, the standard operating software can process 10,000 averages in about two seconds. But because HSAM performs the averages on the hardware, the OceanDirect device driver can process 10,000 averages in 200ms – 10x faster.
Summary
From determining concentration levels of proteins to identifying contaminants in pharmaceutical materials, the Ocean HR2 spectrometer delivers research-grade spectrometer performance in an instrument that works equally well in the lab or on the line, as part of a standalone setup, or as a key subsystem or component within another device.
Rob Morris is with Ocean Insight
